both libcrypto (part of OpenSSL) and cryptoc++ can handle AES encryption. Given you are talking about "server" I suppose you are using OpenSSL already so libcrypto is probably the easier way to go. You can see an example of how to do it here: https://gist.github.com/mythosil/1292328 (yes, it's in C as libcrypto is in C)

@William.Tran That's what we were discussing in the 3 posts above. In you javascript you don't use your key directly but you use a 256bit SHA2 hash of the key as input to the decrypter. To create that hash you can use key = QCryptographicHash::hash(strKey.toUtf8(),QCryptographicHash::Sha256);